This invention relates generally to the field of aerospace structures and, more specifically, to a flexible structural frame, a method for its construction, and a method for its use.
Aircraft have a variety of doors, which are a type of panel, along the exterior surface of the airframe. Examples are the main cabin door, the landing gear doors, the cargo doors, and, in military aircraft, the bomb bay doors. While the exterior surfaces of the doors can be manufactured to be substantially flush with the exterior surface of the airframe, discontinuities will exist between the perimeter of the doors and the exterior surface of the airframe. These discontinuities create opportunities for gaps to exist and/or develop between the doors and the exterior surface. These gaps can be detrimental to an aircraft""s aerodynamic characteristics because they produce drag. Thus, eliminating, or at least mitigating, any gaps between the doors and the exterior surface of the airframe is a significant advantage.
One conventional structural technique used to mitigate the gaps between a door and the exterior surface of the airframe, which are both fairly rigid structures, is to make the perimeter of the door approximately the same size as the opening in the airframe. However, the perimeter of the door may approximate the size of the opening only so closely because some nominal gap is required for the door to be able to operate. Furthermore, if either the door or the airframe deforms during the operation of the aircraft, perhaps due to aerodynamic loads or heat, gaps may form between the door and the exterior of the airframe. Another approach has been to use all out-of-plane sealing devices, such as flex seals, blade seals, or scuff seals. However, these devices can also degrade the aerodynamic characteristics of the aircraft, are dangerous to maintenance workers, and require extensive maintenance. A further approach has been to construct a flexible door. This type of door has a compressible strip fixed between two relatively movable plates that are linked in such a way that they cause the strip to compress or expand as desired. A disadvantage of this approach is that it adds substantial weight to the door, making the door harder to handle and requiring more powerful hydraulic devices than might otherwise be required. Therefore, a need has arisen for a new technique to mitigate the gaps between an aircraft door and the exterior surface of the airframe.
The present invention provides a technique-methods and apparatus-that substantially reduces or eliminates at least some of the disadvantages and problems associated with previously developed gap mitigation techniques. Accordingly, the present invention provides a flexible structural frame, a method for its construction, and a method for its use.
In one embodiment, a flexible structural frame is disclosed. The flexible structural frame includes a structure having a passage, the walls of the passage defining an opening. The flexible structural frame also includes a piece of elastomeric material that has a first surface and a second surface. The first surface of the elastomeric material is coupled to at least one wall of the passage. The flexible structural frame further includes at least one rigid member that is coupled to the elastomeric material and at least one tension bearing member that is coupled to the rigid member, such that the elastomeric material is compressed when the tension applied to the tension bearing member increases.
In another embodiment, a method for constructing a flexible structure is also disclosed. The method includes three steps. Step one calls for forming a piece of elastomeric material that has a first surface and a second surface and that contains at least one rigid member coupled to a tension bearing member. Step two requires forming a passage in a structure, the passage having walls that define an opening. The final step requires coupling the first surface of the elastomeric material to at least one wall of the passage, such that the elastomeric material is compressed when the tension applied to the tension bearing member increases.
The present invention has several technical advantages. One technical advantage is that the flexible structural frame mitigates any gaps between a door of an aircraft and the exterior surface of the airframe. Thus, the aerodynamic characteristics of the aircraft are improved. Another technical advantage is that the flexible structural frame can compress and expand to accommodate for any deformations in either the door or the airframe during the operations of the aircraft. Thus, any gaps that form after the door is closed can be mitigated. A further technical advantage is that the gaps between an aircraft door and airframe can be reduced without adding any additional weight to the door.
Other technical features and advantages will be obvious to one of skill in the art from the following figures, description, and claims.